If the mass number of an atom of an element decreases by 4 and atomic number decreases by two then it is

Decreases in atomic number is observed in:

Staements I: ._zX^4 undergoes 2 alpha -decays, 2 beta -decays (negative beta ) and 2 gamma -decays. As a result, the daughter product is ._z._-2X^(A-B) . Staements II: In alpha -decay, the mass number decreases by 4 unit and atomic number decreases by 2 unit. In beta -decay (negative beta ), the mass number remains unchanged and atomic number increases by 1 unit. In gamma -decay, mass number and atomic number remain unchanged.

Staements I: ._zX^4 undergoes 2 alpha -decays, 2 beta -decays (negative beta ) and 2 gamma -decays. As a result, the daughter product is ._z._-2X^(A-B) . Staements II: In alpha -decay, the mass number decreases by 4 unit and atomic number decreases by 2 unit. In beta -decay (negative beta ), the mass number remains unchanged and atomic number increases by 1 unit. In gamma -decay, mass number and atomic number remain unchanged.

Staements I: ._zX^4 undergoes 2 alpha -decays, 2 beta -decays (negative beta ) and 2 gamma -decays. As a result, the daughter product is ._z-2X^(A-B) . Staements II: In beta -decay, the mass number decreases by 4 unit and atomic number decreases by 2 unit. In beta -decay (negative beta ), the mass number remains unchanged and atomic number increases by 1 unit. In gamma -decay, mass number and atomic number remain unchanged.

Staements I: ._zX^4 undergoes 2 alpha -decays, 2 beta -decays (negative beta ) and 2 gamma -decays. As a result, the daughter product is _(z-2)X^(A-8) . Staements II: In beta -decay, the mass number decreases by 4 unit and atomic number decreases by 2 unit. In beta -decay (negative beta ), the mass number remains unchanged and atomic number increases by 1 unit. In gamma -decay, mass number and atomic number remain unchanged.

Assertion: ""_2X^(A) undergoes 2 alpha -decay and the daughter product is ""_(z-4)Y^(A-8) Reason: In alpha -decay the mass number decreases by 4 and atomic number decreases by 2.

Decrease in atomic number is not observed in

Decrease in atomic number is observed in :